Galileo is necessary

Dominique Detain

Europe is building its own global satellite navigation system, Galileo, which will offer very accurate positioning and timing, under civilian responsibility. This system will be compatible with the two other existing systems, GPS and GLONASS. A user will be able to use the same receiver to calculate his position from signals sent out by any satellites combination, however Galileo will offer to all users a bi frequency system that will allow knowing position within one meter of accuracy, which is unprecedented for an openly accessible service. Apart from extreme circumstances, it will always be available and its users will be informed in a few seconds of a potential disruption of one of the satellites. Thus it will be usable for safety of life applications, requiring the highest security level, such as plane landing, train circulation or car guidance.

Today European users have no other choice than use data provided by the American GPS or Russian GLONASS to know their position. But military operators of both systems don’t wish to give any guarantee on the continuity of service. Satellite localization has become the standard for high sea navigation and it will soon be the case for terrestrial transports and air traffic. If it would happen one day that the signal be disrupted a lot of sailors would find it difficult to go back to conventional methods of sailing and to use old almanacs and sextants to calculate their positions. In a few years, when satellite positioning will be generalized, the consequences of a signal disruption will be worse, endangering not only the efficiency of transports systems but also the security of people.

As early as beginning of the 90s, European Union understood how important it was that Europe has its own worldwide satellite navigation system. The decision to develop such a system can be compared to decisions taken in the seventies to launch other big European projects like Ariane or Airbus. The European Commission and the European Space Agency have therefore joined forces to create Galileo, an independent system, under civilian control and whose quality will be permanently guaranteed.

The Global Navigation Satellite System will allow the emergence of new value added services and products meant for road, rail, air and maritime transports but also for professional applications such as fishing, precision farming, oil prospecting etc. Furthermore it will become a crucial tool for civil protection.

Social and economic spin-offs from Galileo, in Europe as in the world at large, are huge. They will notably come from the additional capacities that this system will bring to GNSS.

Until now the design, development and in orbit validation phase have been co- financed by the European Commission and the European Space Agency and it has been recently decided that the deployment of the overall system will be also financed by public money, the private sector coming into the picture for operations once the system is fully installed.

A first Galileo satellite was launched in December 2005. This satellite named GIOVE A (Galileo In Orbit Validation Element) marked the concrete start of Galileo in space. This successful launch allowed to secure the frequencies allocated to Galileo within the International Telecommunications Union and also to check critical technologies currently under development for the Galileo system. Indeed before having a full system operational on orbit it is mandatory to double check any new technology since in the very hostile environment of space there is no way back, this is why everything has to be achieved step by step. For example with GIOVE A, and GIOVE B to be launched this spring 2008, new types of atomic clocks are tested, a key issue since time is at the heart of any satellite navigation system.

The Galileo clocks will be accurate from 1 nanosecond to 10 nanoseconds over 24 hours! Also the particular orbit chosen for

the satellites has to be understood since it
is the first time Europe launches a satellite in what is called the Medium Earth Orbit, at 23222 km of altitude, and it is necessary to monitor the radiation encountered so as to characterize this specific environment and therefore build the operational satellites accordingly. The lessons learnt from this phase are taken for the following step: four satellites to be launched to validate the basic design of the Galileo constellation and its associated ground segment.

The first results from GIOVE A in space are very encouraging since they are in line with what was expected giving confidence that Europe can achieve it! When this “In Orbit Validation” phase will be done the remaining satellites will be launched to get to full operations capacity. Once fully deployed the Galileo constellation will comprise 30 satellites (27 operational and 3 backup), posted on 3 orbital planes with an inclination of 56° with the equator. This will ensure a perfect coverage of our planet with the help of a network of stations distributed all around the earth, Galileo being the first complete civil satellite navigation system. Waiting for Galileo, Europe is already working in the satellite navigation field: ESA, with the European Commission and Eurocontrol, is developing EGNOS (European Geostationary Navigation Overlay Service). This is a network of ground stations correcting and processing GPS signals and transmitting the improved data via geostationary satellites. Compatible with equivalent systems in the world such as WAAS in the US or MSAS in Japan, EGNOS is now in pre-operational service for non safety of life applications and will be later certified for safety of life services. With EGNOS Europe can already show its know how in satellite navigation with the European Industry engaged in working in this promising new technologies whilst at the same time a strong community of users can start developing many value added services, notably in the transport domain. Already with EGNOS many applications have been demonstrated from tracking the riders on the Tour de France to guiding the blind persons, virtual tolling on highways and monitoring rail traffic.This development of EGNOS is a tremendous experience, paving the way for Galileo. But of course if GPS is disrupted EGNOS will warn about it but will not be able to continue on its own… This is why the second step, Galileo, is necessary!

When operational, Galileo will allow a full set of services: from the Open service, similar to what GPS provides today but with a better accuracy, to services that GPS, a military system, cannot or does not want to offer: Commercial services, Safety of Life for civil aviation , maritime transport etc. and also Search and Rescue service: a person in distress will be able to send an SOS associated to its position in quasi real time, a message that will be acknowledged and the S & R team will be able to intervene rapidly in a very well defined area.

And finally the Public regulated service will be at the discretion of each European Union government for its ambulance, its customs, and its police forces. Galileo will be this new and safe tool made in Europe for Europe and beyond, whose foundations are currently being built by the European Space Agency.